Which country are you from, because easy differs from country to country. Have you looked at www.sparkfun.com -> searchbox on the left -> type dac<enter> and several will appear. [my grandparents would have called it magic]

check the mcp4725 - http://www.sparkfun.com/products/8736 - sample code is available

Anything outside of 5V will need additional power supply.The sparkfun part does 25mA, which is not bad. I believe http://www.gravitech.us/ also has a little DAC, look in this section,http://www.gravitech.us/micro-interface-boards.htmlthat works on I2C or SPI and I think has pins on it already for easy use on a breadboard.